1. Field of the Invention
This invention relates to a method and apparatus for detecting an amount of a cooling medium charged in a refrigeration circulation system used for a refrigerator or an air conditioner.
2. Description of the Related Art
In a refrigeration circulation system 20 including a compressor 21 for compressing a gaseous cooling medium, a condenser 22 for cooling the gaseous cooling medium compressed by the compressor 21 and converting it to a liquid cooling medium, an expansion valve 23 for expanding the cooling medium converted to the liquid cooling medium by the condenser 22 and converting it to an atomized cooling medium, and an evaporator 24 for subjecting the cooling medium atomized by the expansion valve 23 to heat-exchange with air as shown in FIGS. 4 and 5 of the accompanying drawings, it is known that when the liquid cooling medium on the inlet side of the expansion valve 23 is appropriately super-cooled, a coefficient of performance of the refrigeration circulation system 20 can be improved.
To super-cool the liquid cooling medium on the inlet side of the expansion valve 23, the cooling medium must be suitably charged into the refrigeration circulation system 20.
However, if an excess amount of cooling medium is charged, the liquid cooling medium at the inlet of the expansion valve 23 will have an excess degree of super-cooling, and the coefficient of performance will be deteriorated. Accordingly, it is necessary to detect whether or not a suitable degree of super-cooling is attained when the cooling medium is first charged into the refrigeration circulation system or when it is added.
As disclosed in Japanese Unexamined Patent Publication (Kokai) No. 3-177762, for example, a detector for detecting the degree of super-cooling uses a pressure sensor, a temperature sensor and a computation means. This detector detects the pressure of the cooling medium downstream of the compressor by the use of the pressure sensor and calculates a temperature T1 of supercooling to 0.degree. C. after the condenser at this detected pressure. An actual temperature T2, after the condenser, is detected by the temperature sensor, and the difference between the temperatures T2 and T1 is calculated so as to detect the degree of super-cooling.
However, the detector for detecting the degree of super-cooling according to the prior art described above involves a problem in that it is expensive because it requires the temperature sensor, the pressure sensor and the computation means.